Wales secured their first Grand Slam for 27 years, first win over Ireland since 1993 and their first championship title for 11 seasons with a 32-20 triumph in Cardiff.
And Williams, voted player of the championship, said: "We don't want this Grand Slam to be a one-off.
"We need to go on and develop from this and there is enough youth in the squad to do that.
"We are nowhere near the guys of the 1970s. They won numerous championships and Grand Slams - we have only won one. It's an honour just to be compared to those guys."
The 54-times capped Williams added: "As well as championships there is the 2007 World Cup.
"We can't say whether we are going to win it but hopefully we would go one better than the quarter-finals."